Relationships of the New Guinean subspecies, Gymnorhina tibicen papuana, of the Australian Magpie: an assessment from DNA sequence data

ABSTRACT

Although it is well understood that New Guinea and Australia are essentially one landmass that connects periodically during sea-level fluctuations, the biogeographic history and effects of environmental change for species that span the two islands has not been studied in depth. The New Guinean subspecies of the Australian Magpie, Gymnorhina tibicen papuana, is known to share morphological traits with subspecies from north-western and south-western Australia (G. t. longirostris and G. t. dorsalis, respectively). Here, we use molecular data to explore the relationships of the New Guinean subspecies. Mitochondrial DNA supports a close relationship with a previously identified Australian phylogroup, which includes the two western Australian subspecies G. t. longirostris and G. t. dorsalis and western populations of what has been recognised as a northern subspecies G. t. eylandtensis. We infer that the formation of land bridges, most likely during the most recent glacial period, allowed movement of magpies between New Guinea and Australia but not, evidently, involving Cape York Peninsula, which is that part of Australia closest today to the range of G. t. papuana. Dispersal would have ceased following the most recent sea-level rise 16 500 years ago. Overall, our study is consistent with a hypothesis that savannah-associated species dispersed between Australia and New Guinea via a western route across land bridges associated with the Sahul Shelf.

KEYWORDS:

• Plumage
• biogeography
• population
• subspecies
• passerines
• evolution
• Australian birds

Acknowledgements

This study would not have been possible without the generous assistance of many people and governmental authorities in Papua New Guinea and Queensland. In Papua New Guinea we are indebted to: Barnabas Wilmott (Papua New Guinea Conservation and Environment Protection Authority); Andrew Moutu and Bulisa Iova and other staff at the Papua New Guinea National Museum and Art Gallery; Georgia Kaipu, Marie Ann Sundie and Jim Robins (National Research Institute); the staff of Bensbach Lodge and all who assisted us in Morehead, Western Province, and Mark Nizette (Department of Environment, Australia). In Queensland we are grateful to Jacqui Brock for assisting in the work that was conducted under Permit WISP 11236912. Joshua Peñalba assisted with field work in Queensland. Kathryn Real assisted in collection of the molecular data. Andrew Black and an anonymous reviewer greatly improved the manuscript.